In thermal management for objects, the methods for heat dissipation using mechanical fans, heat pipes or finned heat sink are inefficient and can only reduce the objects to the temperature which is not lower than room temperature.
Thus, manufacturers develop a thermoelectric device utilizing Peltier effect to automatically drive the transfer of heat in a certain direction. The theory, also known as the Peltier effect, is to create a heat difference from a voltage, by a current passing through two different metals connected to each other at two junctions. The current causes a heat transfer from one junction to the other where one cools off while the other heats up. The flowing of the electric current may carry away the heat of the objects and thus the junction which absorbs the heat may be cooled down to go below the room temperature. The heat flux Q, heat absorbed by the junction per unit time, is equal to: Q=ΠI where Π is the Peltier coefficient; I is the applied current.
An operating electronic device is placed next to the thermoelectric device and the heat of the electronic device is absorbed by the thermoelectric device so that the electronic device may be cooled off. Such thermoelectric device is quiet when operating, without moving mechanical parts, highly reliable, and can be integrated with semiconductor process. Therefore, the thermoelectric device is applied to cool electronic and photoelectric devices. In addition, the thermoelectric device using the Peltier effect in thermal management can accommodate appliances such as portable refrigerators, pocket-size thermo cups, and portable dehumidifiers limited in compact configuration, for better operations thereof.
The thermoelectric device configured to utilize the Peltier effect is generally formed of an array of P and N-type thermoelectric elements. The P and N-type thermoelectric elements are connected electrically to each other in series and thermally in parallel together, so thermal and electrical resistances occur at the junction of the metal electrode and thermoelectric elements. With reducing thermoelectric element thickness, the interfacial contact resistance becomes a key factor that can modulate the performance of the thermoelectric device significantly. The electrical resistance cause joule heat and the thermal resistance make heat backflow worsened, so that the heat-dissipating efficiency of the thermoelectric device is reduced.